tree 9dfc915ef98293b7a7b3e42b7a5de9797b0ceb29
parent 2d5e94d7ca315f859a0eee1366838e8ad34dd7b2
author Henrique de Moraes Holschuh <hmh@hmh.eng.br> 1209182541 -0300
committer Len Brown <len.brown@intel.com> 1209476821 -0400

ACPI: thinkpad-acpi: fix brightness dimming control bug

ibm-acpi and thinkpad-acpi did not know about bit 5 of the EC backlight
level control register (EC 0x31), so it was always forced to zero on
any writes.

This would disable the BIOS option to *not* use a dimmer backlight level
scale while on battery, and who knows what else (there are two other
control bits of unknown function).

Bit 5 controls the "reduce backlight levels when on battery" optional
functionality (active low).  Bits 6 and 7 are better left alone as well,
instead of being forced to zero.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>